J/MNRAS/462/4197ivo://CDS.VizieR/J/MNRAS/462/4197doi:10.26093/cds/vizier.74624197CDSCurran S.J.Duchesne S.W.Divoli A.Allison J.R.2024-08-16T20:18:43Z2018-06-11T15:25:18ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frh-i-line-emissionquasarsredshiftedradio-astronomyThe star-forming reservoir in the distant Universe can be detected through HI 21-cm absorption arising from either cool gas associated with a radio source or from within a galaxy intervening the sightline to the continuum source. In order to test whether the nature of the absorber can be predicted from the profile shape, we have compiled and analysed all of the known redshifted (z>=0.1) HI 21-cm absorption profiles. Although between individual spectra there is too much variation to assign a typical spectral profile, we confirm that associated absorption profiles are, on average, wider than their intervening counterparts. It is widely hypothesized that this is due to high-velocity nuclear gas feeding the central engine, absent in the more quiescent intervening absorbers. Modelling the column density distribution of the mean associated and intervening spectra, we confirm that the additional low optical depth, wide dispersion component, typical of associated absorbers, arises from gas within the inner parsec. With regard to the potential of predicting the absorber type in the absence of optical spectroscopy, we have implemented machine learning techniques to the 55 associated and 43 intervening spectra, with each of the tested models giving a >=80 per cent accuracy in the prediction of the absorber type. Given the impracticability of follow-up optical spectroscopy of the large number of 21-cm detections expected from the next generation of large radio telescopes, this could provide a powerful new technique with which to determine the nature of the absorbing galaxy.2016MNRAS.462.4197Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/462/4197CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/462/4197https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/462/4197http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/462/4197https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/462/4197https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/462/4197http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/462/4197GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/462/4197/table1 (The features of the z>=0.1 associated 21-cm absorbers)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/462/4197/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/462/4197/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/462/4197/table1?GETtext/xml+votable180.050000true6.4548181-26.03683810.005555555555555556Cone search capability for table J/MNRAS/462/4197/table2 (The features of the z>=0.1 intervening 21-cm absorbers)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/462/4197/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/462/4197/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/462/4197/table2?GETtext/xml+votable180.050000true17.1118442-0.62337920.0055555555555555566/392 579 1025 1709 2331 2397 2631 3918 4108 4448 4649 4820 4927 4937 5063 5089 5311 5806 5864 5918 5980 6008 6230 6252 6519 6618 6641 7226-7227 7345 8717 8900 9204 9252 9349 9956 9981 10086 10103 10432 10436 10440 10535 10571 10654 10874 10877 10941 11136 11259 11559 11806 12475 12888 13120 13287 13693 13789 14946 14988 15196 15341 16081 16509 17215 17514 17999 18271 18387 18545 18765 18895 19325 21121 22917 22943 23339 25239 25302 25864 25972 26011 26115 26245 26491 26614 27378 27650 27689 27894 28003 28265 28407 29072 30010 30844 31686 32724 34210 36417 41059 44658https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/462/4197?format=asciiRadiodefaultJ/MNRAS/462/4197/table1The features of the z>=0.1 associated 21-cm absorbersSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIAUIAU namemeta.id;meta.maincharzweight? Mean-weighted absorption redshiftsrc.redshiftdoublenullableng? Number of Gaussian components required to fit the spectrummeta.numberintnullableFWZI? Full width at zero intensityspect.line.widthintnullabletaupeak? Peak observed optical depthphys.absorption.opticalDepth;stat.maxdoublenullableB_taupeak? Maximum peak observed optical depthphys.absorption.opticalDepth;stat.maxdoublenullableb_taupeak? Minimum peak observed optical depthmeta.notedoublenullableDv? Average offset of the components from zweightkm/sobs.param;arith.difffloatnullableDv/FWZI? Average offset of the components from zweight and full width at zero intensitykm/sobs.param;arith.difffloatnullableFWHM? Average full width at half-maximakm/sspect.line.width;stat.meanintnullableB_FWHM? Average full width at half-maximakm/sspect.line.width;stat.meanintnullableb_FWHM? Average full width at half-maximakm/sspect.line.width;stat.meanfloatnullableRefReference for the 21-cm absorption (1)meta.ref;pos.framecharComCommentsmeta.notechar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.mainnullable_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainnullableJ/MNRAS/462/4197/table2The features of the z>=0.1 intervening 21-cm absorbersSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIAUIAU namemeta.id;meta.maincharzweight? Mean-weighted absorption redshiftsrc.redshiftdoublenullableng? Number of Gaussian components required to fit the spectrummeta.numberintnullableFWZI? Full width at zero intensityspect.line.widthintnullabletaupeak? Peak observed optical depthphys.absorption.opticalDepth;stat.maxdoublenullableB_taupeak? Maximum peak observed optical depthphys.absorption.opticalDepth;stat.maxdoublenullableb_taupeak? Minimum peak observed optical depthmeta.notedoublenullableDv? Average offset of the components from zweightkm/sobs.param;arith.difffloatnullableDv/FWZI? Average offset of the components from zweight and full width at zero intensitykm/sobs.param;arith.difffloatnullableFWHM? Average full width at half-maximakm/sspect.line.width;stat.meanintnullableB_FWHM? Average full width at half-maximakm/sspect.line.width;stat.meanintnullableb_FWHM? Average full width at half-maximakm/sspect.line.width;stat.meanfloatnullableRefReference for the 21-cm absorption (1)meta.ref;pos.framecharComCommentsmeta.notechar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.mainnullable_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainnullable